Suspension for a tracked vehicle

ABSTRACT

The present invention relates generally to recreational vehicles. More particularly, the present invention relates to methods and apparatus for traversing challenging terrain with a recreational vehicle. A vehicle in accordance with an exemplary embodiment of the present invention comprises a first drive track that is supported by a first rear suspension and a second drive track of vehicle is supported by a second rear suspension. The first drive track and the second drive track may be operatively coupled to an engine by a drive train for propelling the vehicle.

RELATED APPLICATIONS

This application is related to and claims priority to U.S. provisionalapplication Ser. No. 60/386,025, filed Jun. 4, 2002, and entitled,“Tracked Vehicle.” The present application is also related to a U.S.patent application entitled “Tracked Vehicle” by the same inventor andfiled on an even date herewith. The entire disclosure of theabove-mentioned patent applications is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to recreational vehicles. Moreparticularly, the present invention relates to recreational vehiclesuspensions.

BACKGROUND OF THE INVENTION

In recent years, recreational vehicles have gained widespreadpopularity. Recreational vehicles are commonly used in hunting, trailriding and utility applications such as the wide variety of maintenanceactivities which take place on a farm. Attachments are available whichallow recreational vehicles to be used for plowing snow, mowing grass,hauling material and other useful functions.

Perhaps the most common recreational vehicle application is trailriding. Trail riding on a recreational vehicle allows the rider totravel through areas which are not accessible by ordinary automobiles.Modern recreational vehicles, can cover ground very rapidly and cancover great distances. Frequently, recreational vehicle enthusiasts ridetheir recreational vehicle for many hours straight and cover many miles.If the rider is subjected to excessive jarring while traveling overrough terrain, operator fatigue may result particularly during a longride. During such long rides, a recreational vehicle may be used tocarry a rider through a wide variety of terrain. Terrain that may beencountered includes snow, sand, mud and swampland. Frequentlyrecreational vehicles are called upon to travel across rugged terrain atrelatively high speeds.

Part of the thrill of riding a recreational vehicle is encounteringchallenging terrain, and through the performance of the recreationalvehicle and the skill of the rider passing through the terrain. It isnot uncommon for recreational vehicle riders to seek out large mud holesand attempt to traverse these obstacles with a recreational vehicle. Thedepth of some of these mud holes is actually greater than the height ofthe recreational vehicle. When passing through an obstacle such as mudhole, the recreational vehicle may become immersed in water, mud, or amixture thereof.

SUMMARY OF THE INVENTION

The present invention relates generally to recreational vehicles. Moreparticularly, the present invention relates to methods and apparatus fortraversing challenging terrain with a recreational vehicle. A vehicle inaccordance with an exemplary embodiment of the present inventioncomprises a first drive track that is supported by a first rearsuspension and a second drive track of vehicle is supported by a secondrear suspension. The first drive track and the second drive track may beoperatively coupled to an engine by a drive train for propelling thevehicle. In certain applications, the drive tracks provide a high degreeof traction. The drive tracks may also be arranged to proved arelatively larger foot print which reduces the ground contract pressureof the vehicle.

In certain exemplary embodiments, the first drive track includes aplurality of first bars and the second drive track includes a pluralityof second bars. The first bars of the first drive track having a firstshape and the second bars of the second drive track having a secondshape. In certain advantageous embodiments, the second shape issubstantially a mirror image of the first shape. In some advantageousimplementations, each bar has a generally arcuate shape with a concaveside of each first bar facing a forward direction of the vehicle. Theradius of the bars may be selected for facilitating turning of thevehicle by allowing for lateral slippage of the first drive track andthe second drive track thereby reducing potential damage to turf and/orterrian under the first drive track and the second drive track.

In some exemplary configurations, the vehicle provides for side-by-sideseating of two or more riders. In other configurations the vehicleprovides for tandem (i.e., front to back) seating of two or more riders.

In some useful implementations, the vehicle includes a first actuatorfor varying the characteristics of the first rear suspension (e.g., thespring rate) and a second actuator for varying the characteristics ofthe second rear suspension. In one exemplary embodiment, the firstactuator comprises a first motor and the second actuator comprises asecond motor. In this exemplary embodiment, the first motor and thesecond motor are both electrically coupled to a controller. A firstencoder and a second encoder are also electrically coupled to thecontroller. In certain advantageous embodiments of the presentinvention, the controller is adapted to coordinate the motion of theleft actuator and the right actuator. In these advantageous embodiments,the controller provides an easy way to adjust the suspensioncharacteristics of the vehicle. For example, when hauling heavy loads,it may be desirable to stiffen the rear suspension. Also in theseadvantageous embodiments, the controller assures that the stiffness ofthe first rear suspension will match the stiffness of the second rearsuspension.

A vehicle in accordance with an additional exemplary embodiment of thepresent invention comprises a chassis and a shell attached to thechassis. A pair of front wheels are coupled to the chassis by a frontsuspension. When the vehicle is partially or completely immersed in afluid, the front wheels and the shell provide buoyancy to the vehicle.In one aspect of the present invention, the buoyancy force provided bythe front wheels acts on a front portion of the vehicle and the buoyancyforce provided by the shell acts on a rear portion of the vehicle. Incertain advantageous implementations, the shell is positioned anddimensioned so that these buoyancy forces are balanced about a centroidof the vehicle.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a vehicle having a first seat and asecond seat.

FIG. 2 is an isometric view of a vehicle comprising a handlebar and aseat.

FIG. 3 is a side view of a vehicle in accordance with an additionalexemplary embodiment of the present invention.

FIG. 4 is an isometric view of a vehicle comprising a front wheel thatis supported by a front suspension.

FIG. 5 is a top view of vehicle shown in the previous figure.

FIG. 6 is a bottom view of vehicle shown in the previous figure.

FIG. 7 is a side view of a vehicle comprising a front wheel and a firstdrive track.

FIG. 8 is an additional side view illustrating vehicle shown in theprevious figure.

FIG. 9 is a side view illustrating of a vehicle in accordance with anadditional exemplary embodiment of the present invention.

FIG. 10 is a side view illustrating a vehicle that is partially immersedin a fluid.

FIG. 11 is an isometric view of an assembly in accordance with anexemplary embodiment of the present invention.

FIG. 12 is a diagrammatic representation of a suspension system inaccordance with an exemplary embodiment of the present invention.

FIG. 13 is a side view illustrating of a vehicle in accordance with anadditional exemplary embodiment of the present invention.

FIG. 14 is an enlarged side view illustrating first rear suspension andfirst drive track shown in the previous figure.

FIG. 15 is an additional enlarged side view illustrating first rearsuspension and first drive track shown in the previous figure.

FIG. 16 is an additional enlarged side view illustrating first rearsuspension and first drive track shown in the previous figure.

FIG. 17 is an additional enlarged side view illustrating first rearsuspension and first drive track shown in the previous figure.

FIG. 18 is an isometric view illustrating an assembly in accordance withan additional exemplary embodiment of the present invention.

FIG. 19A is a side view showing a vehicle in accordance with anadditional exemplary embodiment of the present invention.

FIG. 19B is a detail view illustrating a portion of the vehicle shown inthe previous figure.

FIG. 20A is an additional side view illustrating the vehicle shown inthe previous figure.

FIG. 20B is a detail view of an assembly illustrating an additionalexemplary embodiment of the present invention.

FIG. 21 is an additional side view illustrating a vehicle in accordancewith an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

The following detailed description should be read with reference to thedrawings, in which like elements in different drawings are numberedidentically. The drawings, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of theinvention. Examples of constructions, materials, dimensions, andmanufacturing processes are provided for selected elements. All otherelements employ that which is known to those of skill in the field ofthe invention. Those skilled in the art will recognize that many of theexamples provided have suitable alternatives that can be utilized.

FIG. 1 is an isometric view of a vehicle 100 having a first seat 104 anda second seat 106. In the embodiment of FIG. 1, first seat 104 andsecond seat 106 are positioned and dimensioned so as to accommodate twopersons sitting in side-by-side fashion. Vehicle 100 of FIG. 1 includesa front wheel 102 that is connected to a chassis 108 of vehicle 100 by afront suspension 120. Vehicle 100 also includes a first drive track 122and a second drive track 124. In the embodiment of FIG. 1, first drivetrack 122 comprises an endless loop that is supported by a first rearsuspension 126. First drive track 122 may be operatively coupled to anengine by a drive train for propelling vehicle 100. A second drive track124 of vehicle 100 is also visible in FIG. 1. Vehicle 100 also includesa second front wheel 102″ and a steering wheel 128. Steering wheel 128may advantageously be used for steering first front wheel 102 and secondfront wheel 102″.

FIG. 2 is an isometric view of a vehicle 400 comprising a handlebar 430and a seat 432. In the embodiment of FIG. 2, seat 432 shaped to receivetwo riders in tandem. Vehicle 400 of FIG. 2 includes a front ski 434that is connected to a chassis 408 of vehicle 400 by a front suspension420. Vehicle 400 also includes a first drive track 422 that is supportedby a first rear suspension 426. A second drive track 424 of vehicle 400is supported by a second rear suspension 436. First drive track 422 andsecond drive track 424 may be operatively coupled to an engine by adrive train for propelling vehicle 400.

FIG. 3 is a side view of a vehicle 400 in accordance with an additionalexemplary embodiment of the present invention. First drive track 422 andfront ski 434 are visible in FIG. 3. Vehicle 400 of FIG. 3 also includesa seat 432. In the embodiment of FIG. 3, a front portion of seat 432 ispositioned and dimensioned to receive a first rider and a rear portionof seat 432 is dimensioned in positioned to receive a second rider.Vehicle 400 also includes a shell 438 that is fixed to a chassis 408 ofvehicle 400.

In the embodiment of FIG. 3, a forward portion of shell 438 defines aramp 439 that is disposed generally in front of first drive track 422.Ramp 439 may be positioned and dimension so as to pack down terrain(e.g., snow) before that terrain is traversed by drive track 422. Ski434 of vehicle 400 may also be positioned so as to pack down terrainbefore it is encountered by drive track 422. In FIG. 3, ramp 439 isshown defining a ramp angle 429 with a horizontal reference plane. Insome useful embodiments of the present invention, ramp angle 429 isbetween about 5 degrees and about 40 degrees. In some particularlyuseful embodiments of the present invention, ramp angle 429 is betweenabout 10 degrees and about 15 degrees.

FIG. 4 is an isometric view of a vehicle 500 comprising a front wheel502 that is supported by a front suspension 520. Vehicle 500 alsocomprises a first drive track 522 and a second drive track 524. In FIG.4, a first rear suspension 526 of vehicle 500 can be seen disposedwithin an interior 540 defined by an inner surface 542 of drive track544. In the embodiment of FIG. 4 first drive track 522 comprises anendless loop that is supported by a first rear suspension 526. Firstdrive track 522 and second drive track 524 may be operatively coupled toan engine by a drive train for propelling vehicle 500. In the embodimentof FIG. 4, vehicle 500 includes a shell 538 that is preferably fixed tochassis 508 of vehicle 500. In the embodiment of FIG. 4, an outersurface 546 of shell 538 forms a carrier 548 including a cargo carryingsurface 552.

FIG. 5 is a top view of vehicle 500 shown in the previous figure. InFIG. 5, it may be appreciated that shell 538 extends substantiallyacross a width W of vehicle 500. Cargo carrying surface 552 defined byouter surface 546 of shell 538 is also visible in FIG. 5.

FIG. 6 is a bottom view of vehicle 500 shown in the previous figure. InFIG. 6, it may be appreciated that first drive track 522 includes aplurality of first bars 554 and second drive track 524 includes aplurality of second bars 556. First bars 554 of first drive track 522have a first shape and second bars 556 of second drive track 524 have asecond shape. In the embodiment of FIG. 6, the second shape issubstantially a mirror image of the first shape.

In FIG. 6, it may be appreciated that each first bar 554 has a generallyarcuate shape with a concave side 560 of each first bar facing a forwarddirection F. Additionally, each second bar 556 has a generally arcuateshape with a concave side 560 of each first bar facing a forwarddirection F. In the embodiment of FIG. 6, each bar has a radius R. Theshape and position of first bars 554 and second bars 556 may facilitateturning of vehicle 500 by allowing for lateral slippage of first drivetrack 522 and second drive track 524.

FIG. 7 is a side view of a vehicle 600 comprising a front wheel 602 anda first drive track 622. In FIG. 7, a first rear suspension 626 ofvehicle 600 can be seen disposed within an interior 640 defined by aninner surface 642 of first drive track 622. In the embodiment of FIG. 7,first rear suspension 626 is attached to a chassis 608 by a first frontfastener 664 and a first rear fastener 666. In the embodiment of FIG. 7,vehicle 600 includes a shell 638 that is preferably fixed to chassis 608of vehicle 600.

FIG. 8 is an additional side view illustrating vehicle 600 shown in theprevious figure. Shell 638 is shown in cross section in FIG. 8. In theembodiment of FIG. 8, it may be appreciated that an inner surface ofshell 638 defines a cavity 668. Also in FIG. 8, it may be appreciatedthat an outer surface 646 of shell 638 defines a carrier 648 including acargo carrying surface 652. With reference to FIG. 8, it may beappreciated that cargo carrying surface 652 is disposed below a centroid670 of vehicle 600 by a distance D. In certain applications, placingcargo carrying surface 652 in a relatively low location prevents cargoresting on cargo carrying surface 652 from unduly raising a combined(i.e., cargo plus vehicle) center of gravity.

FIG. 9 is a side view illustrating of a vehicle 600 in accordance withan additional exemplary embodiment of the present invention. Vehicle 600of FIG. 9 includes a shell 639 that is fixed preferably fixed to achassis 608 of vehicle 600. Shell 639 is shown in cross section in FIG.9 for purposes of illustration. Vehicle 600 also includes a first frontwheel 602 and a first drive track 622. In the embodiment of FIG. 9,first front wheel 602 comprises a rim 672 and a tire 674. Tire 674defines an enclosed space 676. In FIG. 9 it may be appreciated that alowermost surface 678 of shell 639 is disposed below an uppermostsurface 680 of first front wheel 602 by a distance DB.

FIG. 10 is a side view illustrating a vehicle 600 that is partiallyimmersed in a fluid 682. A first buoyancy force FB is illustrated withan arrow in FIG. 10. In some advantageous embodiments of the presentinvention, first buoyancy force FB is due to the enclosed space 676 of afirst front tire 674 and the enclosed space of a second front tire. Asecond buoyancy force FC is also illustrated with an arrow in FIG. 10.As described above, a vehicle in accordance with certain advantageousembodiments of the present invention includes a shell defining a cavityfilled with air. In the embodiment of FIG. 10, shell 638 producesbuoyancy force FC when it is at least partially immersed in fluid 682.With reference to FIG. 10, it will be appreciated that first buoyancyforce FB is disposed on a front side of a centroid 670 of vehicle 600and second buoyancy force FC is disposed on a rearward side of centroid670.

FIG. 11 is an isometric view of an assembly in accordance with anexemplary embodiment of the present invention. The assembly of FIG. 11includes a cut-away portion of a vehicle chassis 708 defining a firsttunnel 784 and a second tunnel 786. In FIG. 11, it may be appreciatedthat first tunnel 784 and second tunnel 786 are dimensioned to receive afirst rear suspension 726 and a second rear suspension 736 respectively.

In the embodiment of FIG. 11, first rear suspension 726 comprises afirst slide frame 788 including a first slide 790 and a second slide792. In the embodiment of FIG. 11, first rear suspension also comprisesa first front suspension mechanism 794 and a first rear suspensionmechanism 796. As shown in FIG. 11, first front suspension mechanism 794includes a first front suspension arm 798 that is pivotally connected tofirst slide frame 788. Also as shown in FIG. 11, first rear suspensionmechanism 726 includes a first rear suspension arm 802 that is pivotallyconnected to first slide frame 788. In the embodiment of FIG. 11, firstrear suspension arm 802 is pivotally connected to chassis 708 by a firstrear fastener 766. First rear fastener 766 comprises a head 804 that isaccessible from a first side 806 of chassis 708. First rear fastener 766also comprises a shaft 808 that threadingly engages a female threadedmember 820. In some advantageous embodiments of the present invention,female threaded member 820 is fixed to chassis 708. Various methods maybe used to fix female threaded member 820 without deviating from thespirit and scope of the present invention. For example, female threadedmember 820 may be fixed to chassis 708 using screws or rivets. A secondrear suspension arm 822 of second rear suspension 736 is pivotallyconnected to chassis 708 by a second rear fastener 824. Second rearfastener 824 comprises a head (not visible in FIG. 11) that isaccessible from a second side 826 of chassis 708. Second rear fasteneralso comprises a shaft 808 that threadingly engages a female threadedmember 820.

Second rear suspension 736 also comprises a second front suspension arm798 that is pivotally connected to a second slide frame 828. In theembodiment of FIG. 11, second front suspension arm 830 is pivotallyconnected to chassis 708 by a second front fastener 832. Second frontfastener 832 comprises a head (not visible in FIG. 11) that isaccessible from a second side 826 of chassis 708. Second front fastener832 also comprises a shaft 808 that threadingly engages a femalethreaded member 820. First front suspension arm 798 of first frontsuspension 794 is pivotally connected to chassis 708 by a first frontfastener 764. First front fastener 764 comprises a head 804 that isaccessible from a first side 806 of chassis 708. First front fasteneralso comprises a shaft (not visible in FIG. 11) that threadingly engagesa female threaded member.

In an advantageous method in accordance with the present invention,first rear suspension 726 may be disconnected from chassis 708 byremoving first front fastener 764 and first rear fastener 766. Withreference to FIG. 11, it will be appreciated that first front fastener764 and first rear fastener 766 can both be removed from first side 806of chassis 708. Similarly, second rear suspension 736 may bedisconnected from chassis 708 by removing second front fastener 832 andsecond rear fastener 824. In the embodiment of FIG. 11, second frontfastener 832 and second rear fastener 824 can both be removed fromsecond side 826 of chassis 708. Accordingly, a vehicle in accordancewith the present invention may provide for ease of maintenance

FIG. 12 is a diagrammatic representation of a suspension system 1100 inaccordance with an exemplary embodiment of the present invention.Suspension system 1100 comprises a first suspension 1102 and a secondsuspension 1112. First suspension 1102 comprises a first arm 1104 thatis pivotally coupled to a first slide frame 1110. First suspension 1102also comprises a first spring assembly 1138. In the embodiment of FIG.12, a proximal end of first spring assembly is pivotally coupled tofirst arm 1104. A distal end of first spring assembly is pivotallycouple to a first actuator 1106 at a first pivot point 1108. It is to beappreciated that first actuator 1106 may comprise various elementswithout deviating from the spirit and scope of the present invention. Inthe embodiment of FIG. 12, first actuator 1106 comprises a first leadscrew 1116 and a first motor 1118.

Second suspension 1112 comprises a second arm 1122 that is pivotallycoupled to a second slide frame 1140. Second suspension 1112 alsocomprises a second spring assembly 1120. In the embodiment of FIG. 12, aproximal end of second spring assembly 1120 is pivotally coupled tosecond arm 1122. A distal end of second spring assembly is pivotallycouple to a second actuator 1126 at a second pivot point 1124. It is tobe appreciated that second actuator 1126 may comprise various elementswithout deviating from the spirit and scope of the present invention. Inthe embodiment of FIG. 12, second actuator 1126 comprises a second leadscrew 1128 and a second motor 1130.

In the embodiment of FIG. 12, first motor 1118 and second motor 1130 areboth electrically coupled to a controller 1132. A first encoder 1134 anda second encoder 1136 are also electrically coupled to controller 1132.In certain advantageous embodiments of the present invention, controller1132 is configured to receive a first position signal 1142 from firstencoder 1134 and a second position signal 1144 from second encoder 1136.Also in certain advantageous embodiments, controller 1132 includes ameans for comparing first position signal 1142 and second positionsignal 1144.

Controller 1132 may be advantageously configured to provide a firstcontrol signal 1146 and to first motor 1118 and a second control signal1148 to second motor 1130. In some advantageous embodiments of thepresent invention, first control signal 1146 and second control signal1148 are responsive to the comparison of first position signal 1142 andsecond position signal 1144. In certain advantageous embodiments of thepresent invention, controller 1132 is adapted to coordinate the motionof a left actuator and a right actuator. In these advantageousembodiments, the controller provides an easy way to adjust thesuspension characteristics (e.g., spring rate) of the vehicle. Forexample, when hauling heavy loads, it may be desirable to stiffen therear suspension. Also in these advantageous embodiments, the controllerassures that the stiffness of the first rear suspension will match thestiffness of the second rear suspension.

In FIG. 12, an input device 1133 is shown connected to controller 1132.Input device 1133 may be configure to provide an input signal 1135 tocontroller 1132. It is to be understood that input device 1133 maycomprise various elements without deviating from the spirit and scope ofthe present invention. Input device 1133 may comprise, for example, aninput switch.

FIG. 13 is a side view illustrating of a vehicle 2150 in accordance withan additional exemplary embodiment of the present invention. Vehicle2150 comprises a first front wheel 2152 and a first drive track 2154that is supported by a first rear suspension 2156. A momentary contactpoint PA of first front wheel and a momentary contact point PB of firstdrive track 2154 define a ground contact plane 2158 of vehicle 2150.

With reference to FIG. 13, it will be appreciated that first drive track2154 is disposed about a drive sprocket 2160, an upper idler wheel 2162and a lower idler wheel 2164 such that first drive track 2154 assumes agenerally triangular shape. An inner surface 2166 of first drive track2154 and ground contact plane 2158 of vehicle 2150 define a leadingangle AA. Also with reference to FIG. 13, it will be appreciated thatinner surface 2166 of first drive track 2154 and ground contact plane2158 of vehicle 2150 define a trailing angle AB. A lower track angle Axis also illustrated in FIG. 13. As shown in FIG. 13, lower track angleAC is defined by inner surface 2166 of first drive track 2154.

In some advantageous embodiments of the present invention, first drivetrack 2154 assumes a first shape when first rear suspension 2156 is in areference state and a second shape when first rear suspension 2156 isdeflected. In the embodiment of FIG. 13, first rear suspension 2156 isshown in a reference state. Various reference states are possiblewithout deviating from the spirit and scope of the present invention.For example, one reference state may be found when vehicle 2150 is atrest and the weight of vehicle 2150 is supported at least in part byfirst rear suspension 2156. Another example of a reference state may befound when vehicle 2150 is at rest and the weight of both a rider andvehicle 2150 are supported at least in part by first rear suspension2156.

In the embodiment of FIG. 13, first drive track 2154 is supported by adrive sprocket 2160, an upper idler wheel 2162 and a lower idler wheel2164. In the embodiment of FIG. 13, drive sprocket 2160 is rotatablysupported by a chassis 2168 of vehicle 2150. In the embodiment of FIG.13, upper idler wheel 2162 and lower idler wheel 2164 are rotatablysupported by a slide frame 2170 of first rear suspension 2156. In FIG.13, lower idler wheel 2164 is shown extending below upper idler wheel2162.

In the embodiment of FIG. 13, first rear suspension 2156 comprises astrut 2172 that is pivotally coupled to chassis 2168 of vehicle 2150 ata pivot axis T. In the embodiment of FIG. 13, strut 2172 comprises acoil spring 2174 and a damper 2178. First rear suspension 2156 alsoincludes a suspension arm 2182 comprising a first leg 2184 and a secondleg 2186. A proximal portion of second leg 2186 is pivotally coupled tochassis 2168 of vehicle 2l50 at a pivot axis S.

First rear suspension 2156 of FIG. 13 also includes a spring assembly2188. One end of spring assembly 2188 is pivotally coupled to a distalportion of first leg 2184 of suspension arm 2182 at a pivot axis R.Another end of spring assembly 2188 is pivotally coupled to chassis 2168of vehicle 2150 at a pivot axis V. In the embodiment of FIG. 13, springassembly 2188 comprises a shock absorber 2180 and a spring 2176 disposedabout shock absorber 2180.

Drive sprocket 2160 is shown disposed about a drive shaft 2190. In theembodiment of FIG. 13, drive sprocket 2160 and drive shaft 2190 bothrotate about a rotational axis N. In FIG. 13, a longitudinal axis ofsecond leg 2186 of suspension arm 2182 is shown extending belowrotational axis N. Also in FIG. 13, a longitudinal axis of strut 2172can be seen extending above rotational axis N. In some advantageousembodiments of the present invention, the longitudinal axis of secondleg 2186 of suspension arm 2182 extends below rotational axis N and thelongitudinal axis of strut 2172 extends above rotational axis N when thefirst rear suspension is in a fully compressed state. Also in someadvantageous embodiments of the present invention, the longitudinal axisof second leg 2186 of suspension arm 2182 extends below rotational axisN and the longitudinal axis of strut 2172 extends above rotational axisN when the first rear suspension is in a fully extended state.

FIG. 14 is an enlarged side view illustrating first rear suspension 2156and first drive track 2154 shown in the previous figure. In theembodiment of FIG. 14, first rear suspension 2156 is shown in areference state. Also in the embodiment of FIG. 14, first drive track2154 is shown assuming a first shape.

In the embodiment of FIG. 14, first rear suspension 2156 comprises asuspension arm 2182 and a strut 2172. In the exemplary embodiment ofFIG. 14, suspension arm 2182 comprises a first leg 2184 and a second leg2186. A distal portion of second leg 2186 is pivotally connected to aslide frame 2170 at a pivot axis Q. A distal portion of first leg 2184is pivotally connected to a spring assembly 2188 at a pivot axis R.Suspension arm 2182 is pivotally connected to a vehicle chassis at apivot axis S.

A proximal portion of strut 2172 is pivotally coupled to the vehiclechassis at a pivot axis T. A distal portion of strut 2172 is pivotallycoupled to slide frame 2170 at a pivot axis U. In the embodiment of FIG.14, strut 2172 is generally parallel to second leg 2186 of suspensionarm 2182. Also in the embodiment of FIG. 14, the distance between pivotaxis T and pivot axis U is substantially equal to the distance betweenpivot axis S and pivot axis Q.

FIG. 15 is an additional enlarged side view illustrating first rearsuspension 2156 and first drive track 2154 shown in the previous figure.In the embodiment of FIG. 15, first rear suspension 2156 is shown in adeflected state. Also in the embodiment of FIG. 15, first drive track2154 is shown assuming a second shape. The first shape of first drivetrack 2154 is shown with dashed lines in FIG. 15 for purposes ofillustration. With reference to FIG. 15, it will be appreciated that thefirst shape of first drive track 2154 and the second shape of firstdrive track 2154 are both generally triangular.

Drive sprocket 2160 is shown disposed about a drive shaft 2190. In theembodiment of FIG. 15, drive sprocket 2160 and drive shaft 2190 bothrotate about a rotational axis N. In FIG. 15, a longitudinal axis ofsecond leg 2186 of suspension arm 2182 is shown extending belowrotational axis N. Also in FIG. 15, a longitudinal axis of strut 2172can be seen extending above rotational axis N.

FIG. 16 is an additional enlarged side view illustrating first rearsuspension 2156 and first drive track 2154 shown in the previous figure.In the embodiment of FIG. 16, first rear suspension 2156 is shown in adeflected state and first drive track 2154 is shown assuming a secondshape. A reference angular orientation of slide frame 2170 is shown withdashed lines in FIG. 16 for purposes of illustration. The referenceangular orientation illustrated in FIG. 16 generally corresponds to theangular orientation of slide frame 2170 illustrated in FIG. 14.

In some advantageous embodiments of the present invention, slide frame2170 is free rotate about pivot axis Q as suspension first rearsuspension 2156 moves from a reference state to a deflected state. Inthe exemplary embodiment of FIG. 16, slide frame 2170 has rotated by anangle AD. In some embodiments of the present invention, strut 2172 isadapted to expand and contract, thus facilitating rotation of slideframe 2170 about pivot axis Q. In the embodiment of FIG. 16, thedistance between pivot axis S and pivot axis Q is slightly greater thanthe distance between pivot axis T and pivot axis U. Embodiments of thepresent invention are possible in which strut 2172 is biased to assume aposition at which the distance between pivot axis T and pivot axis U issubstantially equal to the distance between pivot axis S and pivot axisQ.

In some advantageous embodiments of the present invention, a trailingangle defined by an inside surface of first drive track 2154 may becomesmaller when first rear suspension 2156 assumes a deflected state. Whenthe trailing angle is relatively large, turning of a vehicle includingfirst rear suspension 2156 may be facilitated. When the trailing angleis relatively small, first drive track 2154 may contact the groundacross a larger footprint area.

FIG. 17 is an additional enlarged side view illustrating first rearsuspension 2156 and first drive track 2154 shown in the previous figure.A reference position of suspension arm 2182 is shown with dashed linesin FIG. 17 for purposes of illustration. The reference positionillustrated in FIG. 17 generally corresponds to the position ofsuspension arm 2182 illustrated in FIG. 14. In some advantageousembodiments of the present invention, suspension arm 2182 is free torotate about pivot axis S as first rear suspension 2156 moves from areference state to a deflected state. In the exemplary embodiment ofFIG. 17, suspension arm 2182 has rotated by and angle AE.

A vehicle in accordance with some useful embodiments of the presentinvention comprises the at least one lower idler wheel that is biasedaway from a chassis of the vehicle by a first suspension force having afirst spring rate and at least one upper idler wheel that is biased awayfrom the chassis by a second suspension force having a second springrate. In some advantageous embodiments, the first spring rate is greaterthan the second spring rate.

FIG. 18 is an isometric view illustrating an assembly in accordance withan additional exemplary embodiment of the present invention. Theassembly of FIG. 18 includes a first drive track 3154 that is disposedabout a drive sprocket 3160, a first idler wheel 3192 and a second idlerwheel 3194 such that first drive track 3154 assumes a generallytriangular shape. In the embodiment of FIG. 18, first idler wheel 3192and second idler wheel 3194 are rotatably supported by a slide frame3170.

The assembly of FIG. 18 also includes a suspension arm 3182 comprising afirst leg 3184 and a second leg 3186. A proximal portion of second leg3186 may be pivotally coupled to a chassis of a vehicle so as to pivotabout a pivot axis S. The assembly of FIG. 18 also includes a springassembly 3188. One end of spring assembly 3188 is pivotally coupled to adistal portion of first leg 3184 of suspension arm 3182 at a pivot axisR. Another end of spring assembly 3188 may be pivotally coupled to achassis of a vehicle. In the embodiment of FIG. 18, spring assembly 3188comprises a shock absorber 3180 and a spring 3176 disposed about shockabsorber 3180.

FIG. 19A is a side view showing a vehicle 4150 in accordance with anadditional exemplary embodiment of the present invention. Vehicle 4150comprises a first front wheel 4152 and a first drive track 4154 that issupported by a first rear suspension 4156. With reference to FIG. 19A,it will be appreciated that first drive track 4154 is disposed about adrive sprocket 4160, a first idler wheel 4192, a second idler wheel 4194and a third idler wheel 4196 such that first drive track 4154 assumes aparallelogram-like shape. In the embodiment of FIG. 19A, vehicle 4150 isshown traversing a hardpack surface 4200. A larger arrow 4202 is shownin FIG. 19A to illustrate a portion of the weight of vehicle 4150 thatis supported by a portion of first drive track 4154 proximate firstidler wheel 4192. In some advantageous embodiments of the presentinvention, first rear suspension 4156 is configured such that onehundred percent to seventy five percent of the weight of vehicle 4150 issupported by a portion of first drive track 4154 proximate first idlerwheel 4192. A smaller arrow 4204 is shown in FIG. 19A to illustrate aportion of the weight of vehicle 4150 that is supported by a portion offirst drive track 4154 proximate second idler wheel 4194. In someadvantageous embodiments of the present invention, first rear suspension4156 is configured such that zero percent to twenty five percent of theweight of vehicle 4150 is supported by a portion of first drive track4154 proximate second idler wheel 4194.

FIG. 19B is a detail view illustrating a portion of a vehicle 4150 shownin the previous figure. In the embodiment of FIG. 19B, first drive track4154 of vehicle 4150 is shown traversing relatively soft terrain 4206.Soft terrain 4206 may comprise, for example, soft soil, snow, sand, andthe like. With reference to FIG. 19B, it will be appreciated that aportion of first drive track 4154 proximate first idler wheel 4192 haspenetrated terrain 4206 to a greater extent than a portion of firstdrive track 4154 proximate second idler wheel 4194. Two arrows are usedto illustrate the pressure applied between first drive track 4154 andterrain 4206. In some advantageous embodiments of the present invention,pressure is distributed substantially evenly across a portion of firstdrive track 4154 extending between first idler wheel 4192 and secondidler wheel 4194 when vehicle 4150 is traversing relatively softterrain.

In the embodiment of FIG. 19B, a portion of first drive track 4154defines a trailing angle 4210 with a horizontal reference plane 4212. Insome useful embodiments of the present invention, trailing angle 4210 isbetween about zero degrees and about thirty degrees. In someparticularly useful embodiments of the present invention, trailing angle4210 is between about zero degrees and about ten degrees.

FIG. 20A is an additional side view illustrating vehicle 4150 shown inthe previous figure. In the embodiment of FIG. 20A, vehicle 4150 isshown traversing a hardpack surface 4200. In the embodiment of FIG. 20,hardpack surface 4200 and a portion of first drive track 4154 define atrailing angle 4210. In some useful embodiments of the presentinvention, trailing angle 4210 is between about zero degrees and aboutthirty degrees. In some particularly useful embodiments of the presentinvention, trailing angle 4210 is between about zero degrees and aboutten degrees. A contact zone 4214 is illustrated in FIG. 20A. In theembodiment of FIG. 20A, contact zone 4214 comprises a portion of firstdrive track 4154 proximate first idler wheel 4192.

In the embodiment of FIG. 20A, vehicle 4150 comprises a first frontwheel 4152 and a first drive track 4154 that is supported by a firstrear suspension 4156. With reference to FIG. 20A, it will be appreciatedthat first drive track 4154 is disposed about a drive sprocket 4160, afirst idler wheel 4192, a second idler wheel 4194 and a third idlerwheel 4196 such that first drive track 4154 assumes a parallelogram-likeshape.

FIG. 20B is a detail view of an assembly illustrating an additionalexemplary embodiment of the present invention. The assembly of FIG. 20Bincludes a first lower idler wheel 5164, a second lower idler wheel5164′, an upper idler wheel 5162, a third idler wheel 5196, and a drivesprocket 5160. A first drive track 5154 is disposed about first loweridler wheel 5164, second lower idler wheel 5164′, upper idler wheel5162, third idler wheel 5196, and drive sprocket 5160. A contact zone5214 is illustrated in FIG. 20B. In the embodiment of FIG. 20A, contactzone comprises a portion of first drive track 5154 extending proximateand extending between first lower idler wheel 5164 and second loweridler wheel 5164. With reference to FIG. 20A and FIG. 20B, it will beappreciated that the contact zone shown in FIG. 20B is generally largerthan the contact zone shown in FIG. 20A.

FIG. 21 is an additional side view illustrating a vehicle 6150 inaccordance with an exemplary embodiment of the present invention.Vehicle 6150 of FIG. 21 comprises a shell 6216. In the embodiment ofFIG. 21, it may be appreciated that an inner surface of shell 6216defines a cavity 6218. Also in FIG. 21, it may be appreciated that anouter surface 6230 of shell 6216 defines a carrier 6220 including acargo carrying surface 6222. With reference to FIG. 21, it may beappreciated that cargo carrying surface 6222 is disposed below a centerof gravity 6226 of the combined mass of vehicle 6150 and a vehicleoperator by a distance D. In certain applications, placing cargocarrying surface 6222 in a relatively low location prevents cargoresting on cargo carrying surface 6222 from unduly raising a combined(i.e., cargo plus vehicle) center of gravity. In the embodiment of FIG.21, a forward portion of shell 6216 defines a ramp 6228 that is disposedgenerally in front of first drive track 6154. Ramp 6228 may bepositioned and dimension so as to pack down terrain before that terrainis traversed by a drive track of vehicle 6150.

Numerous characteristics and advantages of the invention covered by thisdocument have been set forth in the foregoing description. It will beunderstood, however, that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size and ordering of steps without exceeding the scope of theinvention. The invention's scope is, of course, defined in the languagein which the appended claims are expressed.

1. A vehicle comprising: a chassis; a drive sprocket rotatably supportedby the chassis; a rear suspension comprising a suspension arm and astrut, the suspension arm coupled to a spring assembly and extendingbetween the chassis and a slide frame of the rear suspension, the strutextending between the chassis and the slide frame of the rearsuspension; at least one upper idler wheel rotatably supported by a theslide frame of the rear suspension; at least one lower idler wheelrotatably supported by the slide frame of the rear suspension, at leasta portion of the at least one lower idler wheel extending below the atleast one upper idler wheel; a drive track disposed about the drivesprocket, the at least one upper idler wheel and the at least one loweridler wheel, the slide frame being coupled to the chassis by thesuspension arm, which applies a first suspension force, via the springassembly, to bias the slide frame away from the chassis, and the strut,which applies a second suspension force to bias the slide frame awayfrom the chassis, the second suspension force being different from thefirst suspension force.
 2. The vehicle of claim 1, wherein an innersurface of the drive track and a ground contact plane of the vehicledefine a leading angle.
 3. The vehicle of claim 2, wherein the leadingangle is greater than about zero.
 4. The vehicle of claim 1, wherein aninner surface of the drive track and a ground contact plane of thevehicle define a trailing angle.
 5. The vehicle of claim 4, wherein thetrailing angle is greater than about zero degrees.
 6. The vehicle ofclaim 5, wherein the trailing angle is greater than about zero degreesand less than about ten degrees.
 7. The vehicle of claim 6, wherein thetrailing angle is greater than about zero degrees and less than aboutfive degrees.
 8. The vehicle of claim 1, wherein an inner surface of thedrive track defines a lower track angle.
 9. The vehicle of claim 1,wherein the drive track assumes a first shape when the suspension is atrest and the drive track to assumes a second shape when the suspensionis deflected.
 10. The vehicle of claim 9, wherein the first shape is afirst generally triangular shape and the second shape is a secondgenerally triangular shape.
 11. The vehicle of claim 9, wherein thefirst shape is a first diamond shape and the second shape is a seconddiamond shape.
 12. The vehicle of claim 1, wherein: the first suspensionforce has a first spring rate; the second suspension force has a secondspring rate; and the second spring rate is different from the firstspring rate.
 13. The vehicle of claim 12, wherein the first spring rateis greater than the second spring rate.
 14. The vehicle of claim 13,wherein a ratio of the first spring rate to the second spring rate isgreater than about two.
 15. The vehicle of claim 14, wherein a ratio ofthe first spring rate to the second spring rate is greater than aboutfour.
 16. The vehicle of claim 1, wherein the suspension arm includes afirst leg extending to a first leg end pivotally coupled to the springassembly, and a second leg extending to a second leg end pivotallycoupled to the slide frame, the suspension arm pivotally coupled to thechassis between the first leg and the second leg.
 17. The vehicle ofclaim 1, wherein the strut is biased such that a distance of the strutextension between the chassis and the slide frame is substantially equalto a distance of the suspension arm extension between the chassis andthe slide frame.
 18. The vehicle of claim 1, wherein the suspension armincludes a longitudinal axis extending below a rotational axis of adrive shaft of the vehicle.
 19. The vehicle of claim 1, wherein thestrut includes a longitudinal axis extending above a rotational axis ofa drive shaft of the vehicle.
 20. The vehicle of claim 1, wherein: atrailing angle is defined between a ground contact plane of the vehicleand a portion of the drive track extending between the upper idler wheeland the lower idler wheel; and the strut includes suspensioncharacteristics such that the second suspension force causes thesuspension arm to pivot about the chassis so that the trailing angle isreduced when the suspension arm is deflected.
 21. The vehicle of claim1, wherein: a trailing angle is defined between a ground contact planeof the vehicle and a portion of the drive track extending between theupper idler wheel and the lower idler wheel; and the strut includessuspension characteristics such that the second suspension force causesthe slide frame to pivot about the second end of the suspension arm sothat the trailing angle is maintained when the suspension is deflected.